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89-468: A steam engine is a heat engine that performs mechanical work using steam as its working fluid . The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder . This pushing force can be transformed by a connecting rod and crank into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to

178-523: A Carnot engine is possible, then it could be driven in reverse as a heat pump. Mathematical analysis can be used to show that this assumed combination would result in a net decrease in entropy . Since, by the second law of thermodynamics , this is statistically improbable to the point of exclusion, the Carnot efficiency is a theoretical upper bound on the reliable efficiency of any thermodynamic cycle. Empirically, no heat engine has ever been shown to run at

267-472: A better job of predicting how well real-world heat-engines can do (Callen 1985, see also endoreversible thermodynamics ): As shown, the Curzon–Ahlborn efficiency much more closely models that observed. Heat engines have been known since antiquity but were only made into useful devices at the time of the industrial revolution in the 18th century. They continue to be developed today. Engineers have studied

356-402: A book that was read by Robert Boyle . Boyle and his assistant Robert Hooke improved Guericke's air pump design and built their own. From this, through various experiments, they formulated what is called Boyle's law , which states that the volume of a body of an ideal gas is inversely proportional to its pressure. Soon Jacques Charles formulated Charles' Law , which states that the volume of

445-497: A closed space (e.g., combustion chamber , firebox , furnace). In the case of model or toy steam engines and a few full scale cases, the heat source can be an electric heating element . Boilers are pressure vessels that contain water to be boiled, and features that transfer the heat to the water as effectively as possible. The two most common types are: Fire-tube boilers were the main type used for early high-pressure steam (typical steam locomotive practice), but they were to

534-422: A common four-way rotary valve connected directly to a steam boiler. The next major step occurred when James Watt developed (1763–1775) an improved version of Newcomen's engine, with a separate condenser . Boulton and Watt 's early engines used half as much coal as John Smeaton 's improved version of Newcomen's. Newcomen's and Watt's early engines were "atmospheric". They were powered by air pressure pushing

623-410: A drawback, an advantage of heat engines is that most forms of energy can be easily converted to heat by processes like exothermic reactions (such as combustion), nuclear fission , absorption of light or energetic particles, friction , dissipation and resistance . Since the heat source that supplies thermal energy to the engine can thus be powered by virtually any kind of energy, heat engines cover

712-435: A flywheel and crankshaft to provide rotative motion from an improved Newcomen engine. In 1720, Jacob Leupold described a two-cylinder high-pressure steam engine. The invention was published in his major work "Theatri Machinarum Hydraulicarum". The engine used two heavy pistons to provide motion to a water pump. Each piston was raised by the steam pressure and returned to its original position by gravity. The two pistons shared

801-480: A forward direction in which heat flows from a hot reservoir and flows into a cool reservoir to produce work as the desired product. Refrigerators, air conditioners and heat pumps are examples of heat engines that are run in reverse, i.e. they use work to take heat energy at a low temperature and raise its temperature in a more efficient way than the simple conversion of work into heat (either through friction or electrical resistance). Refrigerators remove heat from within

890-466: A fuel, so the engine efficiency is reasonably defined as The efficiency is less than 100% because of the waste heat Q c < 0 {\displaystyle Q_{c}<0} unavoidably lost to the cold sink (and corresponding compression work put in) during the required recompression at the cold temperature before the power stroke of the engine can occur again. The theoretical maximum efficiency of any heat engine depends only on

979-427: A gas at a constant pressure is proportional to its temperature. Boyle's and Charles' Laws were combined into the ideal gas law . Based on these concepts in 1679 Boyle's associate, Denis Papin , built a bone digester , which is a closed vessel with a tightly fitting lid that confines steam until a high pressure is generated. Later designs implemented a steam release valve to keep the machine from exploding. By watching

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1068-453: A gas to a liquid, from liquid to gas, or both, generating work from the fluid expansion or compression. In these cycles and engines the working fluid is always a gas (i.e., there is no phase change): In these cycles and engines the working fluid are always like liquid: A domestic refrigerator is an example of a heat pump : a heat engine in reverse. Work is used to create a heat differential. Many cycles can run in reverse to move heat from

1157-422: A given cylinder size than previous engines and could be made small enough for transport applications. Thereafter, technological developments and improvements in manufacturing techniques (partly brought about by the adoption of the steam engine as a power source) resulted in the design of more efficient engines that could be smaller, faster, or more powerful, depending on the intended application. The Cornish engine

1246-530: A greater efficiency than a Carnot cycle heat engine. Figure 2 and Figure 3 show variations on Carnot cycle efficiency with temperature. Figure 2 indicates how efficiency changes with an increase in the heat addition temperature for a constant compressor inlet temperature. Figure 3 indicates how the efficiency changes with an increase in the heat rejection temperature for a constant turbine inlet temperature. By its nature, any maximally efficient Carnot cycle must operate at an infinitesimal temperature gradient; this

1335-518: A heat engine (which no engine ever attains) is equal to the temperature difference between the hot and cold ends divided by the temperature at the hot end, each expressed in absolute temperature . The efficiency of various heat engines proposed or used today has a large range: The efficiency of these processes is roughly proportional to the temperature drop across them. Significant energy may be consumed by auxiliary equipment, such as pumps, which effectively reduces efficiency. Although some cycles have

1424-416: A large extent displaced by more economical water tube boilers in the late 19th century for marine propulsion and large stationary applications. Many boilers raise the temperature of the steam after it has left that part of the boiler where it is in contact with the water. Known as superheating it turns ' wet steam ' into ' superheated steam '. It avoids the steam condensing in the engine cylinders, and gives

1513-407: A partial vacuum by condensing steam under a piston within a cylinder. It was employed for draining mine workings at depths originally impractical using traditional means, and for providing reusable water for driving waterwheels at factories sited away from a suitable "head". Water that passed over the wheel was pumped up into a storage reservoir above the wheel. In 1780 James Pickard patented the use of

1602-403: A piston into the partial vacuum generated by condensing steam, instead of the pressure of expanding steam. The engine cylinders had to be large because the only usable force acting on them was atmospheric pressure . Watt developed his engine further, modifying it to provide a rotary motion suitable for driving machinery. This enabled factories to be sited away from rivers, and accelerated

1691-432: A set speed, because it would assume a new constant speed in response to load changes. The governor was able to handle smaller variations such as those caused by fluctuating heat load to the boiler. Also, there was a tendency for oscillation whenever there was a speed change. As a consequence, engines equipped only with this governor were not suitable for operations requiring constant speed, such as cotton spinning. The governor

1780-520: A significantly higher efficiency . In a steam engine, a piston or steam turbine or any other similar device for doing mechanical work takes a supply of steam at high pressure and temperature and gives out a supply of steam at lower pressure and temperature, using as much of the difference in steam energy as possible to do mechanical work. These "motor units" are often called 'steam engines' in their own right. Engines using compressed air or other gases differ from steam engines only in details that depend on

1869-413: A steam jet usually supplied from the boiler. Injectors became popular in the 1850s but are no longer widely used, except in applications such as steam locomotives. It is the pressurization of the water that circulates through the steam boiler that allows the water to be raised to temperatures well above 100 °C (212 °F) boiling point of water at one atmospheric pressure, and by that means to increase

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1958-626: A steam rail locomotive was designed and constructed by steamboat pioneer John Fitch in the United States probably during the 1780s or 1790s. His steam locomotive used interior bladed wheels guided by rails or tracks. The first full-scale working railway steam locomotive was built by Richard Trevithick in the United Kingdom and, on 21 February 1804, the world's first railway journey took place as Trevithick's steam locomotive hauled 10 tones of iron, 70 passengers and five wagons along

2047-722: A thermally sealed chamber at low temperature and vent waste heat at a higher temperature to the environment and heat pumps take heat from the low temperature environment and 'vent' it into a thermally sealed chamber (a house) at higher temperature. In general heat engines exploit the thermal properties associated with the expansion and compression of gases according to the gas laws or the properties associated with phase changes between gas and liquid states. Earth's atmosphere and hydrosphere —Earth's heat engine—are coupled processes that constantly even out solar heating imbalances through evaporation of surface water, convection, rainfall, winds and ocean circulation, when distributing heat around

2136-410: A thermodynamic cycle is an ideal case of a mechanical engine. In any case, fully understanding an engine and its efficiency requires a good understanding of the (possibly simplified or idealised) theoretical model, the practical nuances of an actual mechanical engine and the discrepancies between the two. In general terms, the larger the difference in temperature between the hot source and the cold sink,

2225-417: A tradeoff has to be made between power output and efficiency. If the engine is operated very slowly, the heat flux is low, T ≈ T ′ {\displaystyle T\approx T'} and the classical Carnot result is found but at the price of a vanishing power output. If instead one chooses to operate the engine at its maximum output power, the efficiency becomes This model does

2314-611: A trio of locomotives, concluding with the Catch Me Who Can in 1808. Only four years later, the successful twin-cylinder locomotive Salamanca by Matthew Murray was used by the edge railed rack and pinion Middleton Railway . In 1825 George Stephenson built the Locomotion for the Stockton and Darlington Railway . This was the first public steam railway in the world and then in 1829, he built The Rocket which

2403-404: A typical combustion location (internal or external), they can often be implemented with the other. For example, John Ericsson developed an external heated engine running on a cycle very much like the earlier Diesel cycle . In addition, externally heated engines can often be implemented in open or closed cycles. In a closed cycle the working fluid is retained within the engine at the completion of

2492-558: A very limited lift height and were prone to boiler explosions . Savery's engine was used in mines, pumping stations and supplying water to water wheels powering textile machinery. One advantage of Savery's engine was its low cost. Bento de Moura Portugal introduced an improvement of Savery's construction "to render it capable of working itself", as described by John Smeaton in the Philosophical Transactions published in 1751. It continued to be manufactured until

2581-470: A water pump for draining inundated mines. Frenchman Denis Papin did some useful work on the steam digester in 1679, and first used a piston to raise weights in 1690. The first commercial steam-powered device was a water pump, developed in 1698 by Thomas Savery . It used condensing steam to create a vacuum which raised water from below and then used steam pressure to raise it higher. Small engines were effective though larger models were problematic. They had

2670-622: A wide range of applications. Heat engines are often confused with the cycles they attempt to implement. Typically, the term "engine" is used for a physical device and "cycle" for the models. In thermodynamics , heat engines are often modeled using a standard engineering model such as the Otto cycle . The theoretical model can be refined and augmented with actual data from an operating engine, using tools such as an indicator diagram . Since very few actual implementations of heat engines exactly match their underlying thermodynamic cycles, one could say that

2759-424: Is because any transfer of heat between two bodies of differing temperatures is irreversible, therefore the Carnot efficiency expression applies only to the infinitesimal limit. The major problem is that the objective of most heat-engines is to output power, and infinitesimal power is seldom desired. A different measure of ideal heat-engine efficiency is given by considerations of endoreversible thermodynamics , where

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2848-431: Is cylinder condensation and re-evaporation. The steam cylinder and adjacent metal parts/ports operate at a temperature about halfway between the steam admission saturation temperature and the saturation temperature corresponding to the exhaust pressure. As high-pressure steam is admitted into the working cylinder, much of the high-temperature steam is condensed as water droplets onto the metal surfaces, significantly reducing

2937-413: Is limited by a weight placed on the safety valve lever. If the pressure exceeds this limit, the safety valve will be forced open and steam will escape until the pressure drops sufficient for the weight to close the valve again. It is probable that this essential attachment to the steam boiler had previously been used for other purposes; but Papin is given the credit of having first made use of it to control

3026-959: Is positive because isothermal expansion in the power stroke increases the multiplicity of the working fluid while Δ S c {\displaystyle \Delta S_{c}} is negative since recompression decreases the multiplicity. If the engine is ideal and runs reversibly , Q h = T h Δ S h {\displaystyle Q_{h}=T_{h}\Delta S_{h}} and Q c = T c Δ S c {\displaystyle Q_{c}=T_{c}\Delta S_{c}} , and thus Q h / T h + Q c / T c = 0 {\displaystyle Q_{h}/T_{h}+Q_{c}/T_{c}=0} , which gives Q c / Q h = − T c / T h {\displaystyle Q_{c}/Q_{h}=-T_{c}/T_{h}} and thus

3115-399: Is then pumped back up to pressure and sent back to the boiler. A dry-type cooling tower is similar to an automobile radiator and is used in locations where water is costly. Waste heat can also be ejected by evaporative (wet) cooling towers, which use a secondary external water circuit that evaporates some of flow to the air. River boats initially used a jet condenser in which cold water from

3204-465: The Rumford Medal , the committee said that "no one invention since Watt's time has so enhanced the efficiency of the steam engine". In addition to using 30% less steam, it provided more uniform speed due to variable steam cut off, making it well suited to manufacturing, especially cotton spinning. The first experimental road-going steam-powered vehicles were built in the late 18th century, but it

3293-414: The piston or turbine machinery alone, as in the beam engine and stationary steam engine . As noted, steam-driven devices such as the aeolipile were known in the first century AD, and there were a few other uses recorded in the 16th century. In 1606 Jerónimo de Ayanz y Beaumont patented his invention of the first steam-powered water pump for draining mines. Thomas Savery is considered the inventor of

3382-566: The steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines , where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle . In general usage, the term steam engine can refer to either complete steam plants (including boilers etc.), such as railway steam locomotives and portable engines , or may refer to

3471-622: The tramway from the Pen-y-darren ironworks, near Merthyr Tydfil to Abercynon in south Wales . The design incorporated a number of important innovations that included using high-pressure steam which reduced the weight of the engine and increased its efficiency. Trevithick visited the Newcastle area later in 1804 and the colliery railways in north-east England became the leading centre for experimentation and development of steam locomotives. Trevithick continued his own experiments using

3560-409: The working body of the engine while transferring heat to the colder sink until it reaches a lower temperature state. During this process some of the thermal energy is converted into work by exploiting the properties of the working substance. The working substance can be any system with a non-zero heat capacity , but it usually is a gas or liquid. During this process, some heat is normally lost to

3649-514: The 1860s to the 1920s. Steam road vehicles were used for many applications. In the 20th century, the rapid development of internal combustion engine technology led to the demise of the steam engine as a source of propulsion of vehicles on a commercial basis, with relatively few remaining in use beyond the Second World War . Many of these vehicles were acquired by enthusiasts for preservation, and numerous examples are still in existence. In

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3738-562: The 1960s, the air pollution problems in California gave rise to a brief period of interest in developing and studying steam-powered vehicles as a possible means of reducing the pollution. Apart from interest by steam enthusiasts, the occasional replica vehicle, and experimental technology, no steam vehicles are in production at present. Near the end of the 19th century, compound engines came into widespread use. Compound engines exhausted steam into successively larger cylinders to accommodate

3827-551: The 19th century, stationary steam engines powered the factories of the Industrial Revolution . Steam engines replaced sails for ships on paddle steamers , and steam locomotives operated on the railways. Reciprocating piston type steam engines were the dominant source of power until the early 20th century. The efficiency of stationary steam engine increased dramatically until about 1922. The highest Rankine Cycle Efficiency of 91% and combined thermal efficiency of 31%

3916-407: The 20th century, where their efficiency, higher speed appropriate to generator service, and smooth rotation were advantages. Today most electric power is provided by steam turbines. In the United States, 90% of the electric power is produced in this way using a variety of heat sources. Steam turbines were extensively applied for propulsion of large ships throughout most of the 20th century. Although

4005-422: The Carnot limit for heat-engine efficiency, where T h {\displaystyle T_{h}} is the absolute temperature of the hot source and T c {\displaystyle T_{c}} that of the cold sink, usually measured in kelvins . The reasoning behind this being the maximal efficiency goes as follows. It is first assumed that if a more efficient heat engine than

4094-410: The Carnot's inequality into exact equality. This relation is also a Carnot cycle equality The efficiency of a heat engine relates how much useful work is output for a given amount of heat energy input. From the laws of thermodynamics , after a completed cycle: In other words, a heat engine absorbs heat energy from the high temperature heat source, converting part of it to useful work and giving off

4183-474: The atmosphere or into a condenser. As steam expands in passing through a high-pressure engine, its temperature drops because no heat is being added to the system; this is known as adiabatic expansion and results in steam entering the cylinder at high temperature and leaving at lower temperature. This causes a cycle of heating and cooling of the cylinder with every stroke, which is a source of inefficiency. The dominant efficiency loss in reciprocating steam engines

4272-402: The boiler and engine in separate buildings some distance apart. For portable or mobile use, such as steam locomotives , the two are mounted together. The widely used reciprocating engine typically consisted of a cast-iron cylinder, piston, connecting rod and beam or a crank and flywheel, and miscellaneous linkages. Steam was alternately supplied and exhausted by one or more valves. Speed control

4361-529: The chimney so as to increase the draw on the fire, which greatly increases engine power, but reduces efficiency. Sometimes the waste heat from the engine is useful itself, and in those cases, very high overall efficiency can be obtained. Steam engines in stationary power plants use surface condensers as a cold sink. The condensers are cooled by water flow from oceans, rivers, lakes, and often by cooling towers which evaporate water to provide cooling energy removal. The resulting condensed hot water ( condensate ),

4450-419: The cold side to the hot side, making the cold side cooler and the hot side hotter. Internal combustion engine versions of these cycles are, by their nature, not reversible. Refrigeration cycles include: The Barton evaporation engine is a heat engine based on a cycle producing power and cooled moist air from the evaporation of water into hot dry air. Mesoscopic heat engines are nanoscale devices that may serve

4539-452: The context of mechanical energy, the concept of the heat engine has been applied to various other kinds of energy, particularly electrical , since at least the late 19th century. The heat engine does this by bringing a working substance from a higher state temperature to a lower state temperature. A heat source generates thermal energy that brings the working substance to the higher temperature state. The working substance generates work in

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4628-496: The cycle whereas is an open cycle the working fluid is either exchanged with the environment together with the products of combustion in the case of the internal combustion engine or simply vented to the environment in the case of external combustion engines like steam engines and turbines . Everyday examples of heat engines include the thermal power station , internal combustion engine , firearms , refrigerators and heat pumps . Power stations are examples of heat engines run in

4717-401: The efficiency of the steam cycle. For safety reasons, nearly all steam engines are equipped with mechanisms to monitor the boiler, such as a pressure gauge and a sight glass to monitor the water level. Many engines, stationary and mobile, are also fitted with a governor to regulate the speed of the engine without the need for human interference. The most useful instrument for analyzing

4806-444: The first commercially used steam powered device, a steam pump that used steam pressure operating directly on the water. The first commercially successful engine that could transmit continuous power to a machine was developed in 1712 by Thomas Newcomen . James Watt made a critical improvement in 1764, by removing spent steam to a separate vessel for condensation, greatly improving the amount of work obtained per unit of fuel consumed. By

4895-413: The globe. A Hadley cell is an example of a heat engine. It involves the rising of warm and moist air in the earth's equatorial region and the descent of colder air in the subtropics creating a thermally driven direct circulation, with consequent net production of kinetic energy. In phase change cycles and engines, the working fluids are gases and liquids. The engine converts the working fluid from

4984-402: The goal of processing heat fluxes and perform useful work at small scales. Potential applications include e.g. electric cooling devices. In such mesoscopic heat engines, work per cycle of operation fluctuates due to thermal noise. There is exact equality that relates average of exponents of work performed by any heat engine and the heat transfer from the hotter heat bath. This relation transforms

5073-462: The higher volumes at reduced pressures, giving improved efficiency. These stages were called expansions, with double- and triple-expansion engines being common, especially in shipping where efficiency was important to reduce the weight of coal carried. Steam engines remained the dominant source of power until the early 20th century, when advances in the design of the steam turbine , electric motors , and internal combustion engines gradually resulted in

5162-489: The hope of finding a place in which he could satisfactorily pursue his favorite studies. Boyle himself had already been long engaged in the study of pneumatics, and had been especially interested in the investigations which had been original with Guericke. He admitted young Papin into his laboratory, and the two philosophers worked together at these attractive problems. He probably invented his "Digester" while in England, and it

5251-410: The larger is the potential thermal efficiency of the cycle. On Earth, the cold side of any heat engine is limited to being close to the ambient temperature of the environment, or not much lower than 300 kelvin , so most efforts to improve the thermodynamic efficiencies of various heat engines focus on increasing the temperature of the source, within material limits. The maximum theoretical efficiency of

5340-425: The late 18th century. At least one engine was still known to be operating in 1820. The first commercially successful engine that could transmit continuous power to a machine was the atmospheric engine , invented by Thomas Newcomen around 1712. It improved on Savery's steam pump, using a piston as proposed by Papin. Newcomen's engine was relatively inefficient, and mostly used for pumping water. It worked by creating

5429-410: The nature of the gas although compressed air has been used in steam engines without change. As with all heat engines, the majority of primary energy must be emitted as waste heat at relatively low temperature. The simplest cold sink is to vent the steam to the environment. This is often used on steam locomotives to avoid the weight and bulk of condensers. Some of the released steam is vented up

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5518-514: The pace of the Industrial Revolution. The meaning of high pressure, together with an actual value above ambient, depends on the era in which the term was used. For early use of the term Van Reimsdijk refers to steam being at a sufficiently high pressure that it could be exhausted to atmosphere without reliance on a vacuum to enable it to perform useful work. Ewing 1894 , p. 22 states that Watt's condensing engines were known, at

5607-453: The performance of steam engines is the steam engine indicator. Early versions were in use by 1851, but the most successful indicator was developed for the high speed engine inventor and manufacturer Charles Porter by Charles Richard and exhibited at London Exhibition in 1862. The steam engine indicator traces on paper the pressure in the cylinder throughout the cycle, which can be used to spot various problems and calculate developed horsepower. It

5696-456: The piston axis in vertical position. In time the horizontal arrangement became more popular, allowing compact, but powerful engines to be fitted in smaller spaces. The acme of the horizontal engine was the Corliss steam engine , patented in 1849, which was a four-valve counter flow engine with separate steam admission and exhaust valves and automatic variable steam cutoff. When Corliss was given

5785-406: The reciprocating steam engine is no longer in widespread commercial use, various companies are exploring or exploiting the potential of the engine as an alternative to internal combustion engines. There are two fundamental components of a steam plant: the boiler or steam generator , and the "motor unit", referred to itself as a "steam engine". Stationary steam engines in fixed buildings may have

5874-413: The replacement of reciprocating (piston) steam engines, with merchant shipping relying increasingly upon diesel engines , and warships on the steam turbine. As the development of steam engines progressed through the 18th century, various attempts were made to apply them to road and railway use. In 1784, William Murdoch , a Scottish inventor, built a model steam road locomotive. An early working model of

5963-510: The rest as waste heat to the cold temperature heat sink. In general, the efficiency of a given heat transfer process is defined by the ratio of "what is taken out" to "what is put in". (For a refrigerator or heat pump, which can be considered as a heat engine run in reverse, this is the coefficient of performance and it is ≥ 1.) In the case of an engine, one desires to extract work and has to put in heat Q h {\displaystyle Q_{h}} , for instance from combustion of

6052-577: The river is injected into the exhaust steam from the engine. Cooling water and condensate mix. While this was also applied for sea-going vessels, generally after only a few days of operation the boiler would become coated with deposited salt, reducing performance and increasing the risk of a boiler explosion. Starting about 1834, the use of surface condensers on ships eliminated fouling of the boilers, and improved engine efficiency. Evaporated water cannot be used for subsequent purposes (other than rain somewhere), whereas river water can be re-used. In all cases,

6141-509: The steam available for expansive work. When the expanding steam reaches low pressure (especially during the exhaust stroke), the previously deposited water droplets that had just been formed within the cylinder/ports now boil away (re-evaporation) and this steam does no further work in the cylinder. Heat engine A heat engine is a system that converts heat to usable energy , particularly mechanical energy , which can then be used to do mechanical work . While originally conceived in

6230-412: The steam plant boiler feed water, which must be kept pure, is kept separate from the cooling water or air. Most steam boilers have a means to supply water whilst at pressure, so that they may be run continuously. Utility and industrial boilers commonly use multi-stage centrifugal pumps ; however, other types are used. Another means of supplying lower-pressure boiler feed water is an injector , which uses

6319-586: The substance going through the reversible Carnot cycle: T h ′ {\displaystyle T'_{h}} and T c ′ {\displaystyle T'_{c}} . The heat transfers between the reservoirs and the substance are considered as conductive (and irreversible) in the form d Q h , c / d t = α ( T h , c − T h , c ′ ) {\displaystyle dQ_{h,c}/dt=\alpha (T_{h,c}-T'_{h,c})} . In this case,

6408-406: The surroundings and is not converted to work. Also, some energy is unusable because of friction and drag . In general, an engine is any machine that converts energy to mechanical work . Heat engines distinguish themselves from other types of engines by the fact that their efficiency is fundamentally limited by Carnot's theorem of thermodynamics . Although this efficiency limitation can be

6497-414: The system is broken into reversible subsystems, but with non reversible interactions between them. A classical example is the Curzon–Ahlborn engine, very similar to a Carnot engine, but where the thermal reservoirs at temperature T h {\displaystyle T_{h}} and T c {\displaystyle T_{c}} are allowed to be different from the temperatures of

6586-488: The temperature of the steam above its saturated vapour point, and various mechanisms to increase the draft for fireboxes. When coal is used, a chain or screw stoking mechanism and its drive engine or motor may be included to move the fuel from a supply bin (bunker) to the firebox. The heat required for boiling the water and raising the temperature of the steam can be derived from various sources, most commonly from burning combustible materials with an appropriate supply of air in

6675-694: The temperatures it operates between. This efficiency is usually derived using an ideal imaginary heat engine such as the Carnot heat engine , although other engines using different cycles can also attain maximum efficiency. Mathematically, after a full cycle, the overall change of entropy is zero:       Δ S h + Δ S c = Δ c y c l e S = 0 {\displaystyle \ \ \ \Delta S_{h}+\Delta S_{c}=\Delta _{cycle}S=0} Note that Δ S h {\displaystyle \Delta S_{h}}

6764-478: The time, as low pressure compared to high pressure, non-condensing engines of the same period. Watt's patent prevented others from making high pressure and compound engines. Shortly after Watt's patent expired in 1800, Richard Trevithick and, separately, Oliver Evans in 1801 introduced engines using high-pressure steam; Trevithick obtained his high-pressure engine patent in 1802, and Evans had made several working models before then. These were much more powerful for

6853-399: The valve rhythmically moving up and down, Papin conceived the idea of a piston and cylinder engine. He did not, however, follow through with his design. In 1697, independent of Papin's designs, engineer Thomas Savery built the world's first steam engine. By 1712 an improved design based on Papin's ideas was developed by Thomas Newcomen . Boyle speaks of Papin as having gone to England in

6942-405: The various heat-engine cycles to improve the amount of usable work they could extract from a given power source. The Carnot cycle limit cannot be reached with any gas-based cycle, but engineers have found at least two ways to bypass that limit and one way to get better efficiency without bending any rules: Each process is one of the following: Steam digester The steam-release valve, which

7031-622: Was demonstrated and published in 1921 and 1928. Advances in the design of electric motors and internal combustion engines resulted in the gradual replacement of steam engines in commercial usage. Steam turbines replaced reciprocating engines in power generation, due to lower cost, higher operating speed, and higher efficiency. Note that small scale steam turbines are much less efficient than large ones. As of 2023, large reciprocating piston steam engines are still being manufactured in Germany. As noted, one recorded rudimentary steam-powered engine

7120-544: Was developed by Trevithick and others in the 1810s. It was a compound cycle engine that used high-pressure steam expansively, then condensed the low-pressure steam, making it relatively efficient. The Cornish engine had irregular motion and torque through the cycle, limiting it mainly to pumping. Cornish engines were used in mines and for water supply until the late 19th century. Early builders of stationary steam engines considered that horizontal cylinders would be subject to excessive wear. Their engines were therefore arranged with

7209-450: Was either automatic, using a governor, or by a manual valve. The cylinder casting contained steam supply and exhaust ports. Engines equipped with a condenser are a separate type than those that exhaust to the atmosphere. Other components are often present; pumps (such as an injector ) to supply water to the boiler during operation, condensers to recirculate the water and recover the latent heat of vaporisation, and superheaters to raise

7298-529: Was entered in and won the Rainhill Trials . The Liverpool and Manchester Railway opened in 1830 making exclusive use of steam power for both passenger and freight trains. Steam locomotives continued to be manufactured until the late twentieth century in places such as China and the former East Germany (where the DR Class 52.80 was produced). The final major evolution of the steam engine design

7387-543: Was first described in a brochure written in English, under the title, "The New Digester." It was subsequently published in Paris. This was a vessel with a safety valve, which can be tightly closed by a screw and a lid. Food can be cooked along with water in the vessel when the vessel is heated, and the vessel's internal temperature can be raised by as much as the pressure inside the vessel will permit safely. The maximum pressure

7476-410: Was improved over time and coupled with variable steam cut off, good speed control in response to changes in load was attainable near the end of the 19th century. In a simple engine, or "single expansion engine" the charge of steam passes through the entire expansion process in an individual cylinder, although a simple engine may have one or more individual cylinders. It is then exhausted directly into

7565-411: Was invented for Papin's digester following various explosions of the earlier models, inspired the development of the piston-and-cylinder steam engine . The artificial vacuum was first produced in 1643 by Italian scientist Evangelista Torricelli and further developed by German scientist Otto von Guericke with his Magdeburg hemispheres . Guerike's demonstration was documented by Gaspar Schott , in

7654-479: Was not until after Richard Trevithick had developed the use of high-pressure steam, around 1800, that mobile steam engines became a practical proposition. The first half of the 19th century saw great progress in steam vehicle design, and by the 1850s it was becoming viable to produce them on a commercial basis. This progress was dampened by legislation which limited or prohibited the use of steam-powered vehicles on roads. Improvements in vehicle technology continued from

7743-495: Was routinely used by engineers, mechanics and insurance inspectors. The engine indicator can also be used on internal combustion engines. See image of indicator diagram below (in Types of motor units section). The centrifugal governor was adopted by James Watt for use on a steam engine in 1788 after Watt's partner Boulton saw one on the equipment of a flour mill Boulton & Watt were building. The governor could not actually hold

7832-758: Was the aeolipile described by Hero of Alexandria , a Hellenistic mathematician and engineer in Roman Egypt during the first century AD. In the following centuries, the few steam-powered engines known were, like the aeolipile, essentially experimental devices used by inventors to demonstrate the properties of steam. A rudimentary steam turbine device was described by Taqi al-Din in Ottoman Egypt in 1551 and by Giovanni Branca in Italy in 1629. The Spanish inventor Jerónimo de Ayanz y Beaumont received patents in 1606 for 50 steam-powered inventions, including

7921-437: Was the use of steam turbines starting in the late part of the 19th century. Steam turbines are generally more efficient than reciprocating piston type steam engines (for outputs above several hundred horsepower), have fewer moving parts, and provide rotary power directly instead of through a connecting rod system or similar means. Steam turbines virtually replaced reciprocating engines in electricity generating stations early in

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